A conventional solid electrolytic capacitor of this type is structured as shown in FIG. 7. In FIG. 7, the solid electrolytic capacitor comprises a valve metal 5 having an anode lead-out part 2 and a capacitor element part 3, a dielectric oxide layer disposed on the valve metal, a conductive high polymer layer disposed on the dielectric oxide layer, a conductor layer disposed on the conductive high polymer layer, an anode terminal 6, a cathode terminal 7, and an external resin 8. The valve metal 5 has a roughened surface or porous layer processed by etching. The anode lead-out part 2 and capacitor element part 3 are separated from each other by a resist material 1 disposed on the surface of the valve metal 5. The dielectric oxide layer is formed by anodic oxidation. The anode terminal 6 is electrically connected to the anode lead-out part 2. The cathode terminal 7 is electrically connected to the conductor layer. The external resin 8 is formed by molding to cover the entire capacitor element.
Herein, the conductive high polymer layer is formed either by a method of forming by electrolytic oxidation polymerization by the use of monomer, or by a method of forming to chemical oxidation polymerization. The electrolytic oxidation polymerization is a method of forming a conductive high polymer layer on the surface of a manganese dioxide layer preliminarily formed on a dielectric oxide layer. The chemical oxidation polymerization is a method of forming a conductive high polymer layer directly on the surface of a dielectric oxide layer.
In the solid electrolytic capacitor shown in FIG. 7, however, the valve metal having the roughened layer or porous layer is divided into the anode lead-out part 2 and capacitor element part 3 by means of the resist material 1, but the conductive high polymer layer contacts with the anode lead-out part 2 through the gap 4 of the roughened layer or porous layer, and defective insulation may occur, or insulation breakdown may take place. Accordingly, it has been proposed to broaden the width of the resist material 1, or use a material having a high adhesion to the valve metal. In such proposals, too, it was difficult to obtain stable effects always in numerous production lots, and achieve a stable and low defective rate of insulation. It was also disadvantageous from the viewpoint of cost.
It is hence an object of the invention to present a solid electrolytic capacitor which can be manufactured in a relatively easy method, and is capable of preventing defective insulation due to conductive high polymer layer reaching up to the anode lead-out portion, and preventing occurrence of insulation breakdown, while maintaining the conventional excellent productivity.